Asynchronous file synchronization of Lightning DB

I run several linux machines and synchronize my files using Unison (http://www.cis.upenn.edu/~bcpierce/unison/) on removable media.  I'm considering using Mozilla Lightning on these machines and want to better understand synchronizing the Lightning DB (calendar-data/local.sqlite).  I cannot keep my calendar in the cloud, so synchronizing with webdav or Google Calendar isn't relevant here.

I'd tremendously getting your input on these questions:

1) When local.sqlite is overwritten by file synchronization, will Lightning detect that event and invalidate any in-memory caching?  Are there any integrity or concurrency issues here?

2) Is it necessary to exit Thunderbird/Lightning before synchronizing?

3) If my calendars get out of sync, is there a batch tool (not GUI) that dumps calendar-data/local.sqlite to an .ICS, and a batch tool (not GUI) that imports a merged .ICS into calendar-data/local.sqlite? 

[Back story: Upon detecting a file hash/timestamp conflict, unison can launch an arbitrary merge tool.  I'd write a script that dumps both Lightning local.sqlite files to ICS, invoke a text file merge tool like meld or ediff-merge, and generate a merged local.sqlite.

4) Am I missing an obviously better, cleaner, and incredibly simpler solution? 

Thanks for any thoughts!